The present invention relates to a metal detector which finds use in, for example, searching hidden metal articles.
U.S. Pat. No. 3,714,563 describes a metal detector appliance in which the emitter resistance value of a transistor is manually set anew before each operation of the appliance.
U.S. Pat. No. 3,453,532 describes a metal detector appliance which operates with negative feedback which sets in with delay. In this case, the adjustment is undertaken by means of a push-button switch. An indicating measuring device is adjusted by a potentiometer.
Furthermore, a device for the indication of faults in a metal piece is described in U.S. Pat. No. 3,688,186. This device operates with a delayed automatic amplifier control.